The major purpose of this study was to explore the effects of different math instruction methods for 3rd grade elementary school students. The subjects were two classes of third-grade students. One of the classes adopted cooperative learning approach of Student Teams Achievement Division (STAD), and the other class adopted the regular math instruction method. After 11 weeks of quasi-experimental teaching, the results were as follows: Cooperative learning (STAD) could promote the effect of math academic achievement for grade 3 elementary school students. Cooperative learning (STAD) could enhance the interest of math for grade 3 elementary school students. Cooperative learning (STAD) could lower dislike for math significantly but not the overall math anxiety degree for grade 3 elementary school students. Cooperative learning (STAD) group students' cooperative skills (helping, listening, encouraging, expressing and participating) were strongly enhanced by the embedded cooperative skill training program.